Interior rearview mirror assemblies which include a directional or compass display are known, such as the types disclosed in U.S. Pat. No. 5,802,727, which is hereby incorporated herein by reference. Typically, such mirror assemblies include a compass sensor, such as a magnetoresistive sensor, a magnetocapacitive sensor, a magnetoinductive sensor, or a flux gate sensor or the like, which is fixedly attached to the mirror mount that attaches the mirror assembly to a mirror assembly mounting element, such as a conventional mounting button mounted on an interior surface of the windshield of the vehicle. The mirror assemblies also include processing circuitry and a compass information display, typically included in the interior mirror casing (that includes the mirror reflector) which is pivotally adjustable by the driver to suit his or her rearward field of view.
Predominantly, compass mirror assemblies in the market today involve the fixed placement of the compass sensor (and any locally associated sensor circuitry), such as at the mirror mount where the mirror attaches to the windshield or headliner of the vehicle. The compass system typically involves a cable/harness connection to the processing circuitry (which is typically in the pivotable housing of the mirror assembly), which may include the compass compensation circuitry and the like, which feeds or connects to a display (such as a vacuum fluorescent (VF) display or the like) that is typically included in the adjustable mirror casing (such as behind the reflective element so as to display from behind and through the reflective element, or at an eyebrow or chin region of the bezel area of the mirror casing). The display then typically displays an output of the directional heading of the vehicle to the driver or passenger of the vehicle, such as an eight octant display, such as N, S, E, W, NE, NW, SE, SW, or the like.
It has been proposed in the art to mount the compass sensor within the movable housing of the rearview mirror assembly. Processes have also been proposed to compensate for movement of the sensor during normal use of the mirror, such as when the mirror head or casing is adjusted by the driver. Such a commercially implemented system, such as currently implemented in a Lexus vehicle and such as described in U.S. Pat. Nos. 6,140,933 and 6,023,229, which are hereby incorporated herein by reference, requires the use of a specially adapted single ball mount or single pivot mirror assembly. Such compass mirror assemblies can be costly and often involve special tooling and complicated adaptation of the mirror assembly itself and the casing of the mirror assembly. Also, such compass systems as described in the patents referenced above are not readily adapted for use with double ball or double pivot mirror assemblies.
It is also known to provide a stand-alone compass pod or module, which may be mounted at the mirror assembly mount at the windshield or headliner of the vehicle. The compass pod includes the compass sensor or sensors and all of the compass circuitry and is operable to output a compensated signal to a display at the instrument panel or console via a cable or wire or the like. However, the display, typically a VF display, has its own logic, circuitry, drivers and/or photosensor input (for adjustment of the display in response to ambient lighting in the vehicle), which may not readily communicate with the circuitry output of the compass pod. In order to convey and/or receive the correct compensated directional signal, a serial or similar encoding or communication protocol may need to be established, so that the compensated directional signal is correctly received by the display equipment in the instrument panel or console. This can result in an expensive compass add-on device, since it may be costly to encode and decode the signals from the compass circuitry.
It is also known to provide a compass display, and associated circuitry, all integrated into a module attaching to an interior rearview mirror assembly, such as disclosed in U.S. Pat. No. 5,576,687, which is hereby incorporated herein by reference in its entirety. While such modules may work well in many applications, such incorporation of the information display of compass direction/heading in the module has disadvantages, including the need to assure readability of the display by the driver of the vehicle.
It is also known in the art (such as disclosed in U.S. Pat. Nos. 6,539,306; 5,724,316; and 5,761,094, which are hereby incorporated herein by reference) to utilize a global positioning system as a means of or adjunct to directional sensing in vehicles. Such known systems either have or seek to overcome problems that can arise when the global positioning system fails to receive appropriate signal inputs from orbiting satellites. Several potential solutions have been proposed that can involve costly and complicated additions to the vehicle.
Therefore, there is a need in the art for an economical interior compass rearview mirror assembly, and particularly an interior compass rearview mirror assembly which is economical to use or implement, such that the assembly may be implemented in non-luxury vehicles, which often use a double ball, prismatic interior rearview mirror assembly.